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Neurologic complications of Influenza A novel H1N1

Neurologic complications of Influenza A novel H1N1. Larry E. Davis, MD Distinguished Professor of Neurology New Mexico VA Health Care System. 9/29/09. N eurologic diseases reported from other influenza A H1N1 strains. Influenza encephalopathy Post-influenza deafness & vertigo

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Neurologic complications of Influenza A novel H1N1

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  1. Neurologic complicationsof Influenza A novel H1N1 Larry E. Davis, MD Distinguished Professor of Neurology New Mexico VA Health Care System 9/29/09

  2. Neurologic diseases reported from other influenza A H1N1 strains • Influenza encephalopathy • Post-influenza deafness & vertigo • Guillain-Barre Syndrome • Influenza myositis

  3. Influenza encephalopathy Occurs mainly in children and teens • World wide but more common in Japan 3 major types • Acute encephalopathy with seizures • Acute disseminated encephalomyelitis • Reyes syndrome

  4. Acute encephalopathy with seizures • Peak incidence: 1-15 years • Common major signs • Fever -- Cough • Seizures --Stupor or coma • Uncommon signs • Paresis, aphasia, choreoathetosis, CN palsies • MRI: Usually normal • Outcome: 2/3rd good recovery, 1/3rd sequelae

  5. Acute encephalopathy with seizures from Influenza A novel H1N1 • Texas & New Mexico cases: 5 • Ages: 7-17 yrs (4M, 1F) • Interval from URI onset to neurologic sx: 1-4 days • Clinical signs • Generalized seizures: 100% (1 status epilepticus) • Delirium or stupor: 100% • Focal neurologic signs: 20% (ataxia) • CSF: acellular, nl glucose, nl protein, virus PCR neg • MRI: normal 100% • Outcome: Full recovery: 4 Unclear: 1

  6. Acute disseminated encephalomyelitis • Peak incidence: 1-5 years • Common major signs • Seizures --Coma • Focal neurologic signs (paresis, aphasia, CN palsies • MRI: multifocal white matter foci • Outcome: 30% died, 10% severe sequelae, 20% mild sequelae No ADEM cases reported yet from Influenza A H1N1

  7. Reye’s syndrome • Definition: severe acute encephalopathy with elevated blood ammonia & liver transaminases • Associated with Influenza B & A mainly from 1965-1985, esp children who ate aspirin • Still reported in Japan • Mortality: 30-40% No Reye’s cases reported yet from Influenza A H1N1

  8. Post-influenza deafness & vertigo • Epidemics of influenza A commonly associated with • Sudden unilateral hearing loss, often permanent • Vertigo lasting about 1 week with good recovery • Occurs mainly in adults with influenza No cases reported yet from Influenza A H1N1

  9. Guillain-Barre syndrome andH1N1 influenza • French observed epidemiologically that some GBS cases were associated with prior influenza-like illnesses & serologic rises to influenza A • U.S. has not reported this association • CDC has asked the VA and neurologists to report all GBS cases that could be associated with influenza this year

  10. Guillain-Barre Syndrome andinfluenza vaccination • GBS incidence: 1-2 cases/100,000/year • 1976 H1N1 vaccine: 3 cases/100,000/year • 1977-2007 flu vaccines: background incidence • New H1N1 vaccine: expected background incidence

  11. Influenza myositis • Symptoms: Focal muscle weakness and pain during influenza mainly in children • Muscle biopsy: focal necrosis and inflammation of muscle fibers • Outcome: Good recovery No cases reported yet from Influenza A H1N1

  12. “I had a little bird and his name was Enza. I opened the window and in-flew-Enza” -1918 poem-

  13. Possible causes of influenza non-respiratory signs and symptoms • Toxic phenomena of viral proteins • Cytokinesreleased from respiratory tract inflammation • Non-permissive viral infectionof systemic organs (brain, liver, muscle, heart, & inner ear)

  14. Brain endothelium Myocardium Non-permissive influenza virus replication (mouse model) Tissues: -Viral antigen detected & RNA detected by PCR -No infectious virus was isolated Skeletal muscle Immunoperoxidase and Immunofluorescent staining with rabbit anti-influenza B/Lee antibody Davis et al Lab Invest 1983

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